Low-cost electrochemical biosensor based on a multi-walled carbon nanotube-doped molecularly imprinted polymer for uric acid detection

Uric acid is a naturally occurring antioxidant that must be maintained in the human body at 1.49–4.46 mM to prevent hyperuricemia, which may lead in the formation of monosodium urate (MSU) and Lesch–Nyhan syndrome. The objective of this research is to examine molecularly imprinted polymers (MIP)-based non-enzymatic electrochemical sensors that simulate the biological mechanism of uricase oxidase. As an affordable working electrode, commercial pencil graphite electrode (PGE) was modified with multi-walled carbon nanotubes (MWCNTs) and polypyrrole. With a 1:10 uric acid to monomer ratio, 20 cycles of polymerization, 100 mV s⁻¹ of polymerization rate, and 30 cycles of template removal, the optimum MIP was obtained. By employing differential pulse voltammetry (DPV) to detect the presence of uric acid over the range of 0.22–3.5 mM, the limit of detection (LOD) was determined to be 0.76 mM, with a sensitivity of 97.459 µA µM⁻¹ cm⁻². This sensor demonstrated good repeatability and reproducibility, with relative standard deviation percentage (%RSD) of 3.43 % (n = 10) and 5.37 % (n = 3), respectively, which maintains a performance stability of 71 % after 19 days of use. This sensor also detected uric acid with good selectivity, even in the presence of interfering molecules including K⁺, Na⁺, sarcosine, citric acid, ascorbic acid, glucose, and dopamine.